The interview looked pretty average, it all started with a conversation with a recruiter. Then was a session with a couple of engineers where I was asked pretty easy questions about iOS basics. Then there was an assignment project that they gave three days to complete and asked to spend around three hours to implement. It was pretty straightforward and I spent about three hours on it. After this I got three different sessions with different engineers asking similar questions with a little more deep dive into them and one architectural part based on the assignment project. At the end I had a conversation with an engineering manager. All sessions took 45 minutes each. It is beyond my understanding how can one assess architectural knowledge in 40 minutes (at least 5 minutes are left in each session for your questions). After all of this I received a call from the recruiter saying that one of the sessions had "mixed" feedback. Whatever this means, they didn't get any expressive feedback and didn't give a chance to improve in future. What worsens the situation is that I was told the feedback wasn't bad it was just levelled not for Staff level and they asked if I'm interested in Senior role in another team. I said I am as I was exited about Slack and confident in my experience and abilities, so I can grow within the company quickly. I then was asked to have a chat with another Engineering Manager. This conversation went smoothly as well. After this I received another call from the recruiter saying that they've decided not to move further. No additional feedback was provided. They managed to reject me twice during one interview, that's a whole new level. The recruiter couldn't explain how it's possible and just repeated a few general phrases. I don't know if it's fair to a candidate and it seems like they either didn't do their due diligence before asking me about another level or one of interviewers simply didn't like me. My personal advice is to be more open and expressive in your feedback. I felt like it was a complete waste of time after such rejection.

You go through a few interviews with them: first with the hiring manager, then an engineer of the same level you're applying for, then a coding exercise. The hiring manager asked me several questions in regards to team fit and communication, of which are great questions to ask for more senior roles. After, I had an interview with a staff engineer and went over pretty basic OOP, CS, and iOS questions. This is mostly to uncover the breadth of knowledge you may have on the platform. Afterwards, I was invited to do a takehome exercise. The process overall went well, however my main gripe was getting a rejection letter with no real feedback. Unfortunately, they do not send feedback regarding the coding exercise due to confidentiality reasons, which I understand; however, it seems like I didn't even really get a chance to explain the decisions I made in an exercise that was supposed to be time-boxed to 3-4 hours. Unfortunately, this experience really tarnished an otherwise stellar interview process, as everyone was quite responsive, amicable, and eager to talk. As part of feedback for the interview process, while specifics aren't necessary, it would be nice to receive high-level feedback on what the issues were that ultimately led to a rejection. I believe there are ways to return feedback that is abstracted enough to where it doesn't break confidentiality of the exercise itself.